org.opendaylight.infrautils.inject.AbstractLifecycle Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of inject Show documentation

Provides support for lifecycle management and dependency injection completion callbacks

There is a newer version: 7.0.3

/*
 * Copyright (c) 2016 Red Hat, Inc. and others. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.infrautils.inject;

import java.util.concurrent.atomic.AtomicReference;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Support class for {@link Lifecycle}. Provides a convenient base
 * implementation including correct thread safety, exception handling and check
 * for accidental unnecessary re-start & stop. Subclasses must implement
 * {@link #start()} & {@link #stop()}.
 *
 * @author Michael Vorburger (with guidance re. AtomicReference from Tom Pantelis)
 */
public abstract class AbstractLifecycle implements Lifecycle {
    private static final Logger LOG = LoggerFactory.getLogger(AbstractLifecycle.class);

    private enum State {
        STARTED, STOPPED
    }

    private final AtomicReference state = new AtomicReference<>(State.STOPPED);

    protected abstract void start() throws Exception;

    protected abstract void stop() throws Exception;

    /**
     * Please implement {@link #start()} instead of overriding this (here intentionally final) method.
     */
    @Override
    @PostConstruct // NOTE: @PostConstruct is *NOT* inherited from interface, so must be here
    @SuppressWarnings("checkstyle:IllegalCatch")
    public final void init() throws ModuleSetupRuntimeException {
        if (state.compareAndSet(State.STOPPED, State.STARTED)) {
            try {
                start();
            } catch (Exception e) {
                throw new ModuleSetupRuntimeException(e);
            }
        } else {
            LOG.warn("Lifecycled object already started; ignoring start()");
        }
    }

    /**
     * Please implement {@link #stop()} instead of overriding this (here intentionally final) method.
     */
    @Override
    @PreDestroy // NOTE: @PostConstruct is *NOT* inherited from interface, so must be here
    @SuppressWarnings("checkstyle:IllegalCatch")
    public final void destroy() throws ModuleSetupRuntimeException {
        if (state.compareAndSet(State.STARTED, State.STOPPED)) {
            try {
                stop();
            } catch (Exception e) {
                throw new ModuleSetupRuntimeException(e);
            }
        } else {
            LOG.warn("Lifecycled object already stopped; ignoring stop()");
        }
    }

    @Override
    public boolean isRunning() {
        return state.get() == State.STARTED;
    }

    protected void checkIsRunning() {
        if (!isRunning()) {
            throw new IllegalStateException("Lifecycled object is already stopped: " + this.toString());
        }
    }

}